jeudi 11 juin 2015

Different Faces of Pluto Emerging in New Images from New Horizons

NASA - New Horizons Mission logo.

June 11, 2015

Image above: These images are displayed at four times the native LORRI image size, and have been processed using a method called deconvolution, which sharpens the original images to enhance features on Pluto. Deconvolution can occasionally introduce "false" details, so the finest details in these pictures will need to be confirmed by images taken from closer range in the next few weeks. All of the images are displayed using the same brightness scale. Image Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

The surface of Pluto is becoming better resolved as NASA’s New Horizons spacecraft speeds closer to its July flight through the Pluto system.

A series of new images obtained by the spacecraft’s telescopic Long Range Reconnaissance Imager (LORRI) during May 29-June 2 show Pluto is a complex world with very bright and very dark terrain, and areas of intermediate brightness in between. These images afford the best views ever obtained of the Pluto system.

Images above: These images, taken by New Horizons’ Long Range Reconnaissance Imager (LORRI), show four different “faces” of Pluto as it rotates about its axis with a period of 6.4 days. All the images have been rotated to align Pluto's rotational axis with the vertical direction (up-down) on the figure, as depicted schematically in the upper left.From left to right, the images were taken when Pluto’s central longitude was 17, 63, 130, and 243 degrees, respectively. The date of each image, the distance of the New Horizons spacecraft from Pluto, and the number of days until Pluto closest approach are all indicated in the figure. Images Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

New Horizons scientists used a technique called deconvolution to sharpen the raw, unprocessed pictures that the spacecraft beams back to Earth; the contrast in these latest images has also been stretched to bring out additional details. Deconvolution can occasionally produce artifacts, so the team will be carefully reviewing newer images taken from closer range to determine whether some of the tantalizing details seen in the images released today persist. Pluto’s non-spherical appearance in these images is not real; it results from a combination of the image-processing technique and Pluto’s large variations in surface brightness.

Since April, deconvolved images from New Horizons have allowed the science team to identify a wide variety of broad surface markings across Pluto, including the bright area at one pole that scientists believe is a polar cap.

“Even though the latest images were made from more than 30 million miles away, they show an increasingly complex surface with clear evidence of discrete equatorial bright and dark regions—some that may also have variations in brightness,” says New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado. “We can also see that every face of Pluto is different and that Pluto’s northern hemisphere displays substantial dark terrains, though both Pluto’s darkest and its brightest known terrain units are just south of, or on, its equator. Why this is so is an emerging puzzle.”

New Horizons LORRI OPNAV4 Observations

Video above: These images show dramatic variations in Pluto's surface features as it rotates. When a very large, dark region near Pluto’s equator appears near the limb, it gives Pluto a distinctly, but false, non-spherical appearance. Pluto is known to be almost perfectly spherical from previous data. Video Credits: : NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

“We’re squeezing as much information as we can out of these images, and seeing details we’ve never seen before,” said New Horizons Project Scientists Hal Weaver, from the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “We’ve seen evidence of light and dark spots in Hubble Space Telescope images and in previous New Horizons pictures, but these new images indicate an increasingly complex and nuanced surface. Now, we want to start to learn more about what these various surface units might be and what’s causing them. By early July we will have spectroscopic data to help pinpoint that.”

New Horizons is approximately 2.9 billion miles (4.7 billion kilometers) from Earth and just 24 million miles (39 million kilometers) from Pluto. The spacecraft and payload are in good health and operating normally.